#include <stdlib.h>
#include <assert.h>

#include "collections.h"

class Node
{
    friend      class DirStack;
public:
                Node( Dir i, Node *n );

private:
    Dir         item;
    Node        *next;
};

Node::Node( Dir i, Node *n )
    : item( i )
    , next( n )
{}

DirStack::DirStack()
    : tos( NULL )
{}

bool DirStack::isEmpty()
{
    return !tos;
}

void DirStack::push( Dir dir )
{
    tos = new Node( dir, tos );
}

Dir DirStack::pop()
{
    assert( !isEmpty() );
    Node *t = tos;
    tos = tos->next;
    Dir res = t->item;
    // delete t;
    return res;
}

Dir DirStack::top()
{
    assert( !isEmpty() );
    return tos->item;
}

void DirStack::print( ostream& os )
{
    for( Node *cur = tos; cur; cur = cur->next ) {
        os << cur->item << " ";
    }

    os << endl;
}